1. Field of the Invention
The present invention relates to instruments and methods of treating spinal conditions, and more particularly to instruments and methods for treating spondylolisthesis, scoliosis, and the like.
2. Description of Related Art
Spondylolisthesis is a spinal disorder that arises from two separate conditions. The first involves a lytic defect in the pars interarticularis, otherwise known as a spondylolysis. The lytic condition most commonly occurs where the lumbar spine meets the sacrum, e.g., at L5-S1. The second condition involves a slippage of the vertebra related to degenerated disc disease and facet arthrosis. The degenerative condition usually involves L4-5 segments. However, spondylolisthesis can occur at any level in the lumbar and less commonly in the cervical spine. Treatment of spondylolisthesis often involves a fusion of the two vertebra involved. Motion sparing technologies, such as total disc replacements, are also used to treat milder cases of degenerative spondylolisthesis.
Spondylolisthesis treatment options routinely include spinal fusion procedures. These can be performed with a combined anterior and posterior approach. The anterior approach is performed via a direct anterior transperitoneal or retroperitoneal approach or lateral approach. This surgery allows direct removal of the majority of the disc, and placement of structural grafts in the disc space. Graft materials include autogenous bone from the iliac crest, allograft, and bone morphogenic protein. The discectomy procedure allows a mobility of the motion segment and enhances fusion rates. This is because anterior grafts are placed under compression as compared to posterior fusion masses, which are under tension. The broad surface area between the endplates allow for higher fusion rates.
The distraction of the collapsed disc space of the listhetic segment allows a mild reduction of the listhesis. This reduction is enhanced by impacting a lordotically shaped graft within the intervertebral space. Alternatively, motion sparing technologies have been used for this problem. Posterior reduction techniques using pedicle screw and rod systems have a significant risk of nerve root traction injuries. None of the traditional instruments, including instruments used in anterior approaches, allow for a combination of both distraction of the disc space and correction of listhesis.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for instrumentation to allow for a combination of distraction of the disc space and correction of the listhesis. There also remains a need in the art for such instrumentation that can be used from anterior and other approaches. The present invention provides a solution for these problems.